Received same email. Interesting part is that I received the email in the evening on May 7. The 'suspicious activity' noted in the email supposedly occured May 8 in the early morning. Good indicator it is spam or Google can now see into the future. Also, the links in the email itself are good spam indicators.
Here is the content of the email I received:
Someone recently tried to use an application to sign in to your Google Account, firstname.lastname@example.org. We prevented the sign-in attempt in case this was a hijacker trying to access your account. Please review the details of the sign-in attempt:
May 8, 2012 2:59am GMT
IP Address: 18.104.22.168
Location: Sunnyvale, California, United States
If you do not recognize this sign-in attempt, someone else might be trying to access your account. You should sign in to your account and reset your password immediately. Find out how at http://support.google.com/accounts?p=reset_pw
If this was you, and you want to give this application access to your account, complete the troubleshooting steps listed at http://support.google.com/mail?p=client_login
The Google Accounts Team
© 2012 Google Inc. 1600 Amphitheatre Parkway, Mountain View, CA 94043
You have received this mandatory email service announcement to update you about important changes to your Google product or account.